The present invention relates in general to data processing systems, and in particular, to displaying image data generated by a fiscal printer used in retail, point of sale operations.
In certain countries, point-of-sale terminal (cash register) printers must have additional hardware that collects and stores that cash register""s sales totals data for reporting tax collection to the government. These printers are known as xe2x80x9cfiscal printersxe2x80x9d. The additional hardware in the fiscal printer that collects and stores these totals is tamper-evident, which is accepted by these governments as xe2x80x9csecurexe2x80x9d. This secure hardware controls print requests to the customer receipt print station from the terminal""s application program, and it also generates printing itself, based on certain circumstances. All printing on customer receipts is also either printed on a separate xe2x80x9cjournalxe2x80x9d paper roll, or stored electronically inside the secure hardware.
Some countries are considering requiring the fiscal printer to control the point of sale (POS) system""s display. The disclosed invention allows the fiscal printer to control some or all of the video display of the POS system with an application program controlling that portion of the system display that is unused. The advent of the all digital display protocols, in particular, would allow one to easily modify the data going to an LCD display to alter a displayed image. In the event that governments require the fiscal printer to control the displayed information on a system display, a method is needed to continue to have an application program display its data while allowing the fiscal printer to modify and display additional information. The present invention discloses a method of changing the interface between a system display controller and a system display so the displayed information may be altered.
The present invention discloses a method and system for having a fiscal printer enabled to control the information displayed on a point of sale (POS) video display. The fiscal printer firmware is modified and additional circuits are added that allow the fiscal printer to load into a memory the image it wants to add to the image displayed by an application program. An overlay controller receives the video controls that provide the signals that determine the start of a scan, how many pixels are in a line and the number of lines. The fiscal printer firmware stores one or more bits of fiscal printer image data in each mapping address of possible pixels of display data. The overlay controller reads the pattern of stored data concurrent with receiving the stored application image. When stored data indicates, application image information going to the system display is modified by the corresponding data stored in the overlay memory device. Different modifications are possible, the data going to the POS display could be color modified, substituted by data stored in the overlay memory device, or changed in other ways determined by the stored data and the code in the fiscal printer microprocessor.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.